This invention results from a need to improve octane ratings for gasoline. Isoparaffin-olefin alkylation is a means to produce highly branched paraffins which effects this octane improvement.
Alkylation is a reaction in which an alkyl group is added to an organic molecule. Thus, an isoparaffin can be reacted with an olefin to provide an isoparaffin of higher molecular weight. Industrially, the concept depends on the reaction of a C.sub.2 to C.sub.5 olefin with isobutane in the presence of an acidic catalyst producing a so-called alkylate. This is a very valuable blending component in the manufacture of gasolines because of its high octane rating.
Traditionally, the process in the industry includes the use of hydrofluoric acid or sulfuric acid and a catalysis carried out under controlled temperature conditions. Low temperatures are utilized in the sulfuric acid process to minimize the side reaction of olefin polymerization and the acid strength is generally maintained at 88 to 94% by the continuous addition of fresh acid and the continuous withdrawal of spend acid The hydrofluoric acid process is less temperature-sensitive and the acid is easily recovered and purified.
The typical types of alkylation currently used to produce high octane blending components, that is, the hydrofluoric acid and sulfuric acid alkylation processes, have inherent drawbacks including environmental concerns, acid consumption and sludge disposal. With the increasing demands for octane and the increasing environmental concerns, it has been desirable to develop an alkylation process based on a solid catalyst system. The catalyst of the present invention offers a refiner a less expensive, more environmentally acceptably and more selective alkylation process than the currently used hydrofluoric and sulfuric acid alkylation processes.
Although alkylation processes using liquid, acidic catalysts are commercially successful, inherent disadvantages arise, in addition to those mentioned above, in the use of such catalysts including handling and disposal of corrosive material.
Consequently, substantial efforts have been made to develop a viable isoparaffin-olefin alkylation process using a solid catalyst, rather than a liquid catalyst, which is commercially acceptable.
U.S. Pat. No. 3,862,258 teaches an alkylation process using a catalyst comprising a macroreticular acid cation exchange resin and boron trifluoride. According to the patent, the life of such a catalyst can be extended by the presence in the reaction mixture of closely controlled amounts of water which can be added to the feed as water or as water-forming compound.
U.S. Pat. No. 3,450,644 discloses a method for regenerating a zeolite catalyst used in hydrocarbon conversion processes involving carbonium ion intermediates.
U.S. Pat. No. 3,549,557 describes alkylation of isobutane with C.sub.2 -C.sub.3 olefins using certain crystalline aluminosilicate zeolite catalysts in a fixed, moving or fluidized bed system.
U.S. Pat. No. 3,644,565 discloses alkylation of a paraffin with an olefin in the presence of a catalyst comprising a Group VIII noble metal present on a crystalline aluminosilicate zeolite. The catalyst is pretreated with hydrogen to promote selectivity.
U.S. Pat. No. 3,647,916 describes an isoparaffinolefin alkylation process featuring use of an ion-exchanged crystalline aluminosilicate, isoparaffin/olefin molar ratios below 3:1 and regeneration of the catalyst.
U.S. Pat. No. 3,655,813 discloses a process for alkylating C.sub.4 -C.sub.5 isoparaffins with C.sub.3 -C.sub.9 olefins using a crystalline aluminosilicate zeolite catalyst wherein a halide adjuvant is used in the alkylation reactor. The isoparaffin and olefin are introduced in to the alkylation reactor at specified concentrations and catalyst is continuously regenerated outside the alkylation reactor.
U.S. Pat. No. 3,706,814 discloses another zeolite-catalyzed isoparaffin-olefin alkylation process and further provides for the addition of C.sub.5 + paraffins such as Udex raffinate or C.sub.5 + olefins to the alkylation reactor feed and the use of specific reactant proportions, halide adjuvants, etc.
U.S. Pat. No. 3,236,671 discloses an alkylation reaction wherein crystalline aluminosilicate zeolites having silica to alumina mole ratios above 3 is used. The reference also discloses the use of various metals exchanged and/or impregnated on such zeolites.
U.S. Pat. No. 3,624,173 discloses an isoparaffinolefin alkylation, which uses crystalline aluminosilicate zeolites containing gadolinium.
U.S. Pat. No. 3,738,977 discloses alkylation of paraffins with ethylene using a zeolite catalyst which possesses a Group VII metal component. The catalyst is pretreated with hydrogen.
U.S. Pat. No. 3,917,738 describes a process for alkylating an isoparaffin with an olefin using a solid, particulate catalyst capable of absorbing the olefin. The isoparaffin and the olefin are admixed to form a reactant stream in contact with catalyst particles at the upstream end of an adsorption zone. Thereafter, the reactants are passed concurrently with the catalyst so that a controlled amount of olefin is adsorbed into the catalyst before the combination of reactants and catalyst is introduced into an alkylation zone. This controlled olefin adsorption is thought to prevent polymerization of the olefin during alkylation.
U.S. Pat. No. 4,384,161 describes a process of alkylating isoparaffins with olefins to provide alkylate using a large pore zeolite catalyst capable of absorbing 2,2,4trimethylpentane, for example ZSM-4, ZSM-20, ZSM-3, ZSM-18, zeolite Beta, faujasite, mordenite, zeolite Y and the rare earth metal-containing forms thereof, and a Lewis acid such as boron trifluoride, antimony pentafluoride or aluminum trichloride. The use of a large pore zeolite with a Lewis acid is reported to increase the activity and selectivity of the zeolite thereby affecting alkylation with high olefin space velocity and low isoparaffin/olefin ratio. According to the patent, problems arise in the use of solid catalysts in that they appear to age rapidly and cannot perform effectively at high olefin space velocity and the patent teaches the above solution to rectify the problem utilizing a zeolite type catalyst.
The article entitled Fixed Bed Catalytic Process to Produce Synthetic Lubricants From Decene-1, Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 4 (1983), teaches oligomerizing olefin to produce fluids with lubricating properties using a silica-BF.sub.3 -water catalyst. The authors further teach that with this system much of the BF3 can be recycled to minimize BF.sub.3 consumption and disposal problems. The reference teaches that water is a necessary component of the system and that in its absence a BF.sub.3 -silica catalyst rapidly deactivates. The reference further teaches that for less reactive olefins, such as Decene-1, a useful degree of oligomerization is achieved only by adding a measurable quantity of an activator such as water or a primary alcohol to B.sub.3. The authors further point out that other BF.sub.3 activators, such as ethers, ketones, acids and anhydrides, have also been claimed to form good olefin oligomerization catalysts. The article states that the process disclosed there is to both minimize BF.sub.3 consumption and disposal problems to produce a product having excellent lubricating properties through use of a catalyst requiring an activator like water.
In U.S. Pat. No. 4,308,414, an olefin, such as 1-decene, is oligomerized in the presence of a three-component catalyst comprising boron trichloride, a minute amount of water and a particulate absorbent material such as silica to a lubricating product predominating in those oligomer fractions having viscosities within the lubricating oil range such as the trimer and tetramer.
U.S. Pat. No. 4,429,177 further relates to a method for making lubricating oil utilizing a catalyst comprising boron trifuoride, a minute amount of elemental oxygen and a particulate absorbent material such as silica. The reference points out that the two component catalyst comprising a solid absorbent and boron trifluoride gradually loses activity after a period of continued use, which aging cannot be conveniently corrected by increasing the boron trifluoride pressure. As a solution, the reference teaches that this aging can be essentially prevented if a minute amount of elemental oxygen is fed to the reactor.
U.S. Pat. No. 3,997,621 relates to oligomerization of olefins catalyzed by boron trifluoride which is controlled to yield desired trimer as a dominant lubricant product by adding small amounts of ester together with water or alcohol promoter.
U.S. Pat. No. 4,365,105, also relates to oligomerizing an olefin in the presence of three-component catalyst used in making lubricating oils which comprises a particular silica absorbent with boron trifluoride and water absorbed on the silica.
U.S. Pat. No. 4,394,296 relates to a three-component catalyst used in making lubricating oils which comprises a particular silica absorbent with boron trifluoride and water absorbed on the silica.
U.S. Pat. No. 2,939,890 discloses a process for alkylating an aromatic hydrocarbon with an olefin-acing compound at alkylation conditions in the presence of an alkylation catalyst comprising boron trifluoride modified alumina. Subsequently, U.S. Pat. No. 3,131,230 discloses the importance of the presence of small amounts of water for maintaining catalyst activity. Both of these patents are limited to aromatic alkylation processes.
U.S. Pat. No. 2,804,491 relates to a isoparaffin/olefin alkylation to make gasoline at temperatures between -20.degree. and 150.degree. F. utilizing a two component catalyst comprising essentially excess BF.sub.3 with a "silica stabilized gel alumina". No activators are taught.
In the past, severe activity and stability problems have been noted with respect to zeolite based systems. U.S. Pat. Nos. 3,251,902 and 3,893,942, as well as French Pat. No. 1,593,716 and the article to Kirsh and Potts, Div. of Pet. Chem. A.C.S., 15, A109 (1970) exemplify these problems. Improved stability was noted when a Lewis acid such as BF.sub.3 was used in combination with macroreticular acid cation exchange resins as pointed out in U.S. Pat. No. 3,855,342. More recently, the use of BF.sub.3 in combination with large pore zeolites such as ZSM-4 and Beta has been reported to effectively catalyze isoparaffin/olefin alkylation reactions. See U.S. Pat. No. 4,384,161. However, only applicants have achieved advantages compared to these previous teachings by the use of a combined isomerization/alkylation process where the alkylation catalyst comprises a Lewis acid, such as BF.sub.3, in combination with a large pore zeolite, such as zeolite Beta and/or non-zeolitic solid inorganic oxide, such as SiO.sub.2 or Al.sub.2 O.sub.3, in the presence of closely controlled amounts of water to produce higher octane gasoline and to reduce catalyst aging.
U.S. Pat. 3,467,728 relates to a process for isomerizing olefinic hydrocarbon, such as 1-butene or 1-pentene by contacting the hydrocarbon with a catalyst comprising a crystalline alumina silicate combined with a substantially anhydrous boron halide.
U.S. Pat. No. 3,800,003 relates to a process for producing an alkylation reaction product from an isoparaffinic reactant and an olefinic reactant containing 1-butene, 2-butene and isobutene which includes passing the olefinic reactant through an isomerization zone. The isomerization catalyst comprises a crystalline aluminosilicate combined with a substantially anhydrous boron halide which can be boron trifluoride. Conventional catalysts are utilized for the alkylation reaction and include sulfuric acid and hydrogen fluoride catalyst which have the disadvantages set forth above.
Chemical abstract No. 145674a refers to an article discussing the effect of moisture and boron fluoride on the catalytic activity of aluminum oxide-boron fluoride. The abstract reports that the degree of catalyst poisoning due to moisture decreases with increasing temperature of catalyst preparation and with BF.sub.3 content in the catalyst. It further reports that the addition of BF.sub.3 into the inlet hydrocarbons prevents the poisoning and regenerates the activity of poisoned catalyst by forming BF.sub.3 .multidot.H.sub.2 O and BF.sub.3 .multidot.H.sub.2 O aducts. The abstract further reports that the effect of moisture in inlet hydrocarbons or in the air during the catalyst preparation and of free BF.sub.3 added into a reactor on the catalytic activity of Al.sub.2 O.sub.3 -BF.sub.3 alkylation catalyst was investigated on the alkylation of C.sub.4 H.sub.10 with propylene.
Thus, this invention overcomes the problems posed by the prior art in that catalyst aging is significantly reduced. Furthermore, this process effects improved octane ratings for gasolines by utilizing a combined isomerization/alkylation process utilizing heterogeneous alkylation catalyst which includes the use of water to active said catalyst.
The preceding references are hereby incorporated by reference.